THE prestigious Melbourne private school at the centre of a student haircut saga has been given three days and a serious ultimatum.

Trinity Grammar students, parents and alumni turned up in their hundreds at an unprecedented meeting on Tuesday night to issue a warning over the sacking of beloved deputy headmaster Rohan Brown.

More than 1000 of those in attendance voted in favour of a no-confidence motion against principal Michael Davies. Fairfax reports just 28 people opposed the vote at Hawthorn Town Hall.

The school's "old boys" - the Old Trinity Grammarians Association - threatened legal action if their demands were not met by Friday.

Students in protest. Picture: Jake Nowakowski

Also at the meeting was the family of the student at the centre of the now week-long protest. His aunt told the meeting that, contrary to earlier statements made by the school, the family never sent a legal letter.

"There was no mention of assault," she said.

Tuesday night's meeting followed a serious escalation on Tuesday when students dressed in casual clothes and held a peaceful protest at the Kew campus attended by hundreds of students. They chanted "We want Browny" and hung signs on fences demanding "Bring Browny back".

A letter from 50 former captains and vice captains at the school from 2001-2017 was sent to the headmaster and the school council chair on Monday night.

"As former Trinity Captains and Vice Captains, we are writing to express our profound disappointment," the letter begins.

The letter to the council board.

The group wrote that they were concerned about "the change in culture and direction of the school".

"In recent years, the school's executive leadership has made clear its intention to change the school's vision and direction.

It's a sentiment shared by current school vice-captain Will Murphy, according to Fairfax. Mr Murphy reportedly told Tuesday night's meeting: "They do not care about us ... they will throw a 15-year-old boy under a bus ... and allow him to be a scapegoat for their agenda."

Mr Brown was forced to resign after a school photo day stunt last Thursday sent the school council into a spin. Mr Brown chopped a student's hair because it did not meet the standards set within the school's grooming guidelines.

Vice Captains spoke in support of Mr Brown last night. Picture: Stuart McEvoy/The Australian

School Council chairman Roderick Lyle wrote to parents last week saying Mr Brown's action was "in contravention of school policy and was also inconsistent with community expectations in this day and age". But support gathered quickly behind Mr Brown.

Many students, teachers and former pupils are calling for the current headmaster and the entire school council to be sacked. A change.org petition calling for the school to reinstate Mr Brown has been signed more than 5000 times.

Mr Brown says he would like to return to the school - a place he's worked for 30 years - if possible.

News.com.au has reached out to Trinity Grammar for comment.

The moment that started it all.

Signed, 50 former captains and vice-captains.

More than 1000 people attended the Town Hall meeting on Tuesday night. Picture: Stuart McEvoy/The Australian